Billboard in VR

I’m trying to use Billboard in version 4.9 with PS4.

However, I met some problems.

First, the billboard will roll with camera, the up vector of billboard is not fixed.
Second, if the billboard has a scene component as root, the scale of root doesn’t affect child billboard’s size.
Third, it seems that I can’t modify billboard’s size by blueprint.
Finally, it seems blinking & flikering obviously if I move location of billboard.